We have assembled a major user group of 5 NIH-funded investigators with 8 projects, and an additional group of 9 minor users, most of whom are also NIH-funded investigators. Our goal is to replace our existing, ~18-year old Hitachi H600 microscope with a JEOL 2100 LaB6 version microscope equipped with a GATAN Ultrascan 1000 digital camera. This microscope has numerous capabilities that our existing instrumentation does not have, among which are digital image acquisition, multi-specimen holder, motorized 5-axis precision goniometer, 200 kV emission current, and remote access microscopy. The software package provided with the high resolution 2K X 2K GATAN camera is the industry standard, and has the capable of generating tomographic reconstructions as well as enabling image acquisition and analysis. In addition, if this application is funded, the MCW administration will purchase a new Boeckler/RMC Ultramicrotome and a Leica EM Pact high pressure freezing system. All of these features will vastly improve the quality and timeliness of the EM work that can be performed at MCW. MCW already has a shared EM facility which will provide the infrastructure and technical expertise for operating, maintaining and using the new equipment. This facility was established by the P.I. in cooperation with Dr. Besharse, one of the other major users, and is ably directed by an electron microscopist with more than 25 years of experience (Mr. Clive Wells). The user group comprises investigators in the Departments of Microbiology & Molecular Genetics, Cell Biology, Neurobiology & Anatomy, Biochemistry, and Medicine. Additional investigators will also be welcome to use the facility as availability permits. Policies regarding instrumentation access and user fees will be reviewed and discussed by an Internal Advisory committee. The new instrumentation will provide MCW with a state-of-the art facility which will provide training and EM services to a broad group of NIH- funded faculty. The work to be performed by the major user group will advance our understanding of the replication and morphogenesis of vaccinia virus (Traktman, 2 projects), the role of the Per3 gene in photoreceptor degeneration and the process of intraflagellar transport of phototransduction proteins in photoreceptors (Besharse, 2 projects), the transcriptional control of gastrointestinal development and hepatic development (Duncan, 2 projects), vertebrate retinal lamination and glaucoma gene interactions (Link, 2 projects), and vibration injury and effect of prolonged spaceflight on human skeletal muscle (Riley, 2 projects). [unreadable] [unreadable]